We compare the results of different ab-initio density-functional methods (Wien97, VASP, ABINIT, PWscf) and approximations for the electronic, structural, and dynamical properties of a variety of single crystals, namely the ionic conductors CaF2, BaF2, ZrO2, and LaF3, and the semiconductors CdS and CdSe. In particular, we have ported the PWscf code to the Hitachi computer. These results are basic for the more extensive and current calculations of the static and lattice-dynamical properties of these systems as well as of systems like ZrO2−δ and mixed-crystal systems like CdSxSe1−x . We also report preliminary neutron scattering data at various temperatures for the structure of LaF3.